1. Field of the Invention
This invention pertains to high pressure delivery liquid systems made of tubing for the transport of liquids, and more particularly to a method and a manifold for transporting liquids at high pressure to supply nozzles for fog, mist or spray production, referred herein to as a misting manifold. This invention also pertains to a more efficient method and system for welding a metallic tubing manifold for liquid transport, the embodiments of the present invention disclosed pertaining to tubing of the sort typically used for misting or atomization manifold systems, thereby more efficiently and economically producing tube manifold having superior joints.
2. Description of Related Art
Misting systems are widely used, they are systems that produce a stream of ultra-fine aerosol-sized droplets of water or other liquids when a mist or a fog is desired. Misting systems are used to keep objects cool or moist, objects such as vegetable produce and, in recent years, misting systems have become more popular for cooling people or animals. Misting systems are also used for theatrical effects to produce fog. The ultra-fine water droplets produced by emitters are introduced into the air where they flash evaporate, dissipating heat and resulting in the cooling of an object. Misting systems used to cool or humidify ambient air are frequently supplemented with a fan or other device to move the misted air about. Such systems may be employed to control environmental conditions in greenhouses, cold storage, outdoor cooling, special effects as well as dust and fire suppression.
Misting systems require that the water or other liquid be forced thorough a specialized nozzle known as an emitter at very high pressure, in a range of about 1,00-3,000 p.s.i., for atomization. The higher pressures are used particularly when ultra fine droplets are required to atomize the water to produce a fog. In general, emitters are attached to a manifold of suitable tubing and liquid is pumped through the tubing to carry the liquid to the emitters to produce the mist or fog. Stainless steel is typically preferred in the manufacture of such systems to prevent corrosion by the liquid, water or salts carried by the liquid.
In the prior art such a manifold might be constructed by providing a length of stainless steel tubing joined to riser. The riser, also made from stainless steel, might be prepared from a billet or from rod stock, as shown in FIGS. 1A-1D. A length of stainless steel tubing 21 of 0.375″ outside diameter, 0.305″ inside diameter and with a wall thickness of about 0.035″ could be used and a hole 22 drilled in the wall of the tube to receive a riser. The riser 23 might also be made from stainless steel and is prepared, shown in FIG. 1B, from a billet or rod stock. The billet is milled to provide a saddle-shaped end 24 to conform to the shape of the tube and a channel or bore 25 is drilled through the axis of the riser; the might additionally be threaded to receive an emitter. The riser channel 25 is then aligned with the hole 22 in the tube and then affixed (in direction of arrow) to the tube with a saddle weld, as shown in FIG. 1D. The hole in the tubing 22 might alternatively be drilled after the welding process, through the riser channel 25, and then through the tube after it is welded to the riser. In either case the hole 22 formed in the tubing wall allows liquid communication between the tubing and the riser channel.
The length of tubing used depends on the specific misting manifold desired. Typically many risers are used in the system and this exercise must be repeated to complete the system. An emitter 99 is screwed into (shown by arrow) the threaded riser channel 25 of each riser.
This construction and method has many disadvantages. The existing process is expensive, time-consuming, difficult to automate and ill-designed to being adapted to use with an orbital welder. Furthermore the existing process usually requires that the welds be made in an uncontained gas environment or even ambient air. An uncontained gas environment using inert gas is one where the welding area is simply flooded with inert gas, allowing lessened but occasional contact with the oxygen from the air. Orbital welding in contrast may be performed in a contained inert gas environment to confine the inert gas. For example, in the Gas Tungsten Arc Welding (GTAW) orbital welding process any inert gas used is contained within the clamshell of the orbital welder and the pieces are welded without contact with oxygen. GTAW is also referred to as TIG (tungsten inert gas) welding.
Moreover, when this prior art method is employed the relative masses of the walls of the riser and the tubing may cause a less desirous weld. The riser is made from stock and must have walls of sufficient thickness to support the emitter. The tubing may have walls that are not as massive and the mass of the riser and the tubing are therefore disproportionate. This disproportionate mass of the parts results in differential heating of the parts during the welding process. Because the riser must be sufficiently heated to weld, the tubing therefore becomes overheated. Excessive heating of the tubing causes deterioration of the metallurgical and structural properties of the tubing, apparently this overheating damages the chemical and structural integrity of stainless steel, rendering it significantly more susceptible to corrosion. The resulting corrosion may in turn lead to clogging of the emitters with corrosion byproducts. Together overheating and contamination by oxygen and associated oxidizing elements during the welding process leads to early corrosion and deterioration of the welded material.
As noted above, each riser must be cut from stock and a saddle shape ground in one end and further be drilled and tapped to receive an emitter. Another drawback to this prior art method is that when more than one riser is placed on a length of tube it is difficult to position the plurality of risers in relative alignment to one another.
It would be advantageous then to manufacture a misting manifold apparatus that is amenable to welding in a contained gas environment, such as with a GTAW/TIG orbital welder, automatedly producing a consistently stronger weld with few contaminants from oxygen. It would also be advantageous to use a construction method an apparatus that joins parts at junctures where the mass of the two parts is similar, to prevent differential heating of the two parts. It would also be advantageous to have a system where individual risers can be more easily relatively aligned when used with the orbital welder.